In scrubbing systems it is necessary to regulate the pH of an aqueous solution therein during their operation. Such systems are typically employed with fossil-fueled electrical generating plant in which particulates and waste gases generated during combustion are removed by a wet-gas scrubbing process in a scrubber chamber. This process involves the injection of a liquid such as water into the scrubber chamber so as to wet the particulates therein. The liquid adds appreciably to the weight of the particulates and causes them to fall countercurrent to the stream of gases. In addition, the liquid is chemically treated to form a solution which chemically reacts and neutralizes the waste gases generated. The amount of chemical added to the liquid is dependent upon the pH level necessary to provide the chemical activity desired. Since the solution admitted into the scrubber chamber is usually recycled, a reliable monitoring system is necessary to constantly transmit the pH of the solution to a control unit. In this manner, the control mechanisms can be operated properly to regulate the pH by varying the chemical content of the solution.
Typically, the monitoring system includes an ion sensor and a reference cell which are exposed to the solution to be monitored. However, as a result of the extreme environment to which the ion sensor is exposed, the ion sensor has a limited lifetime. In particular, the erosion, corrosion, and build-up of particulates to which the sensor unit is subjected severely limits the operation as well as the useful duration of the sensor unit. As a result, the ion sensor requires continuous supervision to assure its proper functioning. This supervision includes frequent physical removal of the ion sensor and cleaning of the build-up of deposits and the scored or scaled surface of the ion sensor as well. In addition, frequent replacement of the ion sensor is required due to wear and tear from the extreme environment to which it is exposed. Such supervision not only increases the operational cost of the system but also degrades the performance as well.
Applicant has invented an improved ion sensor probe which overcomes the above-noted limitations of the prior art.